Topiramate is used basically as an antiepileptic drug; it is effective in migraine prophylaxis, depression, trigeminal neuralgia, bipolar disorders and idiopathic intracranial hypertension. The drug has a large number of ocular side effects such as acute-onset angle closure glaucoma, acute myopia, nystagmus, diplopia, photosensitivity, suprachoroidal effusions, peri-orbital oedema and blepharospasm. We present a patient who was 24-year-old woman presenting with a sudden loss of vision in both eyes. From her medical history, it was learned that the patient started using topiramate twelve days ago. Her uncorrected visual acuities were 20/400 in both eyes and best corrected visual acuities were 20/25 in the right eye with -5.50 spherical refractive correction and 20/20 in the left eye with -6.25 spherical refractive correction. On the second day of the examination, diplopia developed. The patient's clinical condition was considered to be related to the drug and topiramate was discontinued immediately. The clinical findings of the patient improved rapidly without treatment; on the fifth day of the examination, her autorefractometric measurements were +0.25 -0.25 α 121° in her right eye and +0.25 in her left eye; her uncorrected visual acuities were 20/20 in her both eyes and her anterior chamber depths were normal bilaterally. She had no vision complaint and diplopia but she began to complain about photosensitivity. The patient's photosensitivity ceased after 4 months. When the ophthalmologists encounter acute myopia and acute angle closure glaucoma especially in young patients, they should keep in mind the using of topiramate.